Re: Pharmaceuticl Building Grounds
Grounding specifications vary with every engineer who designs a grounding system. There is no standard in the industry other than the minimum standards set forth in the NEC. When you asked the engineer why, his real answer is that this "worked" in another building and therefore must be the correct way.
I have inspected cell sites for 9 different providers and each of them require different types of grounding and bonding, most at least compliant with article 250, yet each is very different. The real reason why is the engineer who designed the system: either he was taught that way (and to unteach someone, commonly called adult education, is the most diffucult task), or it worked somewhere else in this wonderful country and therefore it is the best way to ground. FYI "worked" simply means that a site was hit by lightning and their equipment did not sustain damage. How big or long that strike was, where it actually hit, what its path to the earth was, etc no one actually knows. Also, "did not work" simply means they had an installation where lightning damaged their equipment and therefore had to change the grounding method.
One of the other reasons a certain way of grounding is specified usually is an engineer went to a class and the part he remembers is.....
I do not want to sound like I am bashing engineers. I have the utmost respect for them, the amount of information and the number of resources required combined with the time needed to put it all on paper so someone else can install it is phenominal. Every time I look at a grounding system I look for compliance to the NEC and everything else is just bells and whistles. Either someone sold a bill of goods to a customer, or they actually believe that their way is the best way. Remember, bigger is better. How mant times is a 200 amp service installed when the load calculated is only 60?
Grounding is the one subject that almost everyone has an opinion about, and most of those opinions are based on what they were taught. How good were those teachers? I know I haven't answered your question, so the real answer is that is the way they want it!
Fred Bender
